It is proposed to investigate the relationship between trabecular architecture and stress bearing in bone. Optical data analysis and automatic image analysis will be used to define closely the morphological features of the bony network. Experimental stress analysis, utilizing two- and three-dimensional photoelastic analysis and photoelastic skins will be used to study the mechanical efficiency of the architectural features that are disclosed. It is proposed to utilize these basic studies to investigate two different problems. (a) We expect to obtain information bearing upon the evolution of posture and locomotion in the vertebral column by comparing the big architectural differences in vertebrae of apes and man and associating them with the considerable biomechemical differences in stress bearing that exists in the vertebrae of these species. (b) We expect to obtain information about stress bearing in vertebrae in osteoarthritis and osteoporosis in man, especially for instance, about the extent to which microfractures may be associated, by comparing the smaller architectural differences between normal vertebrae and those found in these disease states with the differences in stress bearing that presumably exist in these conditions. Such studies may well allow us to recognize more easily occult or incipient pathology.